code: def test_flatten():
      """Test the 'flatten' parameter."""
      arr_false = GramianAngularField().transform(X).reshape(1, -1)
      arr_true = GramianAngularField(flatten=True).transform(X)
      np.testing.assert_allclose(
          arr_false, arr_true, atol=1e-5, rtol=0.0
      )
  
file_path: pyts/pyts/image/tests/test_gaf.py
imports: import numpy
  import pytest
  import re
  from pyts.image.gaf import _gasf, _gadf
  from pyts.image import GramianAngularField
label_desc: Use image node_id 5 for calling a global function with example usage: test_flatten() without return types